ixgbe: Fix gso_max_size for 82599 when DCB is enabled

The 32k gso_max_size when DCB is enabled is for 82598 only, not for 82599.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Acked-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>